Impacts of two types of El Niño on the MJO during boreal winter

Pang, Bo; Chen, Zesheng; Wen, Zhiping; Lu, Riyu

doi:10.1007/s00376-016-5272-2

Cited by 26 publications

(24 citation statements)

References 31 publications

(44 reference statements)

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“…This enhanced circulation changes the vertical temperature structure, which can alter the static stability of the upper troposphere/lower stratosphere, which impacts tropical convection anomalies. However, as MJO activity is also modulated by different phases of ENSO (e.g., Marshall et al, 2016;Pang et al, 2016;Pohl & Matthews, 2007) and different phases of the QBO (e.g., Son et al, 2017;Yoo & Son, 2016), disentangling connections from high-latitude processes to tropical convection remains difficult.…”

Section: Results: Causal Graphsmentioning

confidence: 99%

“…Similar predictability was found when looking at output from the Global Environmental multiscale model for connecting the MJO to the NAO (Lin et al, ). Other studies suggest that the connections between the MJO and the NAO may also be a function of other modes which affect the tropospheric waveguide, including the phase of the El Niño–Southern Oscillation (ENSO; e.g., Pang et al, ; Roundy et al, ) and/or the Quasi‐Biennial Oscillation (QBO; e.g., Son et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Tropospheric and Stratospheric Causal Pathways Between the MJO and NAO

et al. 2019

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Previous work has shown that the Madden‐Julian Oscillation (MJO) can influence the North Atlantic Oscillation (NAO) via a Rossby wave teleconnection that propagates through the troposphere (i.e., a tropospheric pathway). In addition, recent work suggests that the MJO can influence the stratospheric polar vortex, which is also known to influence the tropospheric NAO—thus, there likely exists a stratospheric pathway for MJO influence as well. Here, we apply two methods to shed more light on the pathways linking the MJO to the NAO. First, we use a traditional approach in climate science based on analyzing conditional probabilities. Second, we use methods from causal discovery theory based on probabilistic graphical models. Together, these two analysis approaches reveal that the MJO can impact the NAO via both a tropospheric and stratospheric pathway. The stratospheric pathway is shown to come about in two ways: First, both methods show that the MJO itself influences the strength of the stratospheric polar vortex on a timescale of ∼10 days, and then 5 days later the vortex can drive changes in the NAO. Second, the state of the stratospheric polar vortex acts to condition the NAO to be conducive (or not) to MJO influence. When the vortex is in a state that opposes the expected NAO response to the MJO, we find little influence of the MJO on the NAO, however, when the vortex supports the expected NAO response, the NAO is up to 30% more likely to be in a particular state following active MJO periods.

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Section: Results: Causal Graphsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tropospheric and Stratospheric Causal Pathways Between the MJO and NAO

et al. 2019

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“…The QBO is denoted by the reversal of 10-100-hPa equatorial zonal winds between westerly and easterly every 28 months, approximately (Baldwin et al 2001), while ENSO is associated with anomalously warm (El Niño) and cold (La Niña) conditions in the tropical Pacific with a period of 2-8 years (Deser et al 2010). Recent studies have shown that the strength and predictability of the MJO may be modulated by the QBO (Pang et al 2016;Yoo and Son 2016;Son et al 2016). The tropical deep convection during the QBO easterly phase (QBOE) has been found to be much stronger than that during the westerly phase (QBOW), because of different tropopause height, temperature, vertical wind shear, and associated static stability (Collimore et al 2003).…”

Section: Introductionmentioning

confidence: 99%

“…The MJO's strength in the western Pacific is correlated with the eastern extension of the Warm Pool's eastern edge (Kessler 2001;Liess, Bengtsson, and Arpe 2004); and during warm ENSO phases, the convection of the MJO can penetrate further into the central Pacific (Gualdi, Navarra, and Tinarelli 1999;Moon, Wang, and Ha 2011;Liu et al 2016aLiu et al , 2016b. The intensity of the MJO from the tropical eastern Indian Ocean to the western Pacific is weakened during eastern-Pacific El Niño winters, but enhanced during central-Pacific El Niño winters (Feng et al 2014;Pang et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Combined effect of the QBO and ENSO on the MJO

Sun

Wang

Liu

2019

Atmospheric and Oceanic Science Letters

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This study investigates the combined effect of the El Niño-Southern Oscillation (ENSO) and stratospheric quasi-biennial oscillation (QBO) on the Madden Julian Oscillation (MJO). The results show that the western Pacific MJO originating from the Indian Ocean during La Niña/QBO easterly years is stronger than that during El Niño years. This relation, however, disappears during La Niña/QBO westerly years. The reason is that ENSO and the QBO have different effects on each MJO event. For an El Niño year, there is only about one MJO event, and the QBO effect is small. During a La Niña/QBO easterly year, there are 1.7 MJO events, while during a La Niña/QBO westerly year, there are only 0.6 MJO events. El Niño can reinforce the MJO over the western Pacific because of the positive moisture advection of the El Niño mean state by MJO easterly wind anomalies. The QBO mainly affects the MJO over the Maritime Continent region by changing the high-cloud-controlled diurnal cycle; and the Maritime Continent barrier effect is enhanced during the QBO westerly phase because of the strong diurnal cycle. During El Niño years, even the MJO over the Maritime Continent is suppressed by the QBO westerly phase; the MJO can be reinforced over the western Pacific. During La Niña/QBO westerly years, the MJO over the Maritime Continent is suppressed because of the strong Maritime Continent diurnal cycle, and it is further suppressed over the western Pacific because of the lack of a reinforcement process.

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“…5) with several ENSO indices in antecedent winter and spring, the ENSO Modoki (Ashok et al, 2007) in spring (also called the central Pacific ENSO) (cf. Feng et al 2015;Pang et al 2016), and the indices of BFA in June (YT11 and YT14). Additionally, we estimated the correlation with the interannual variation of SCS-SM onset date, which was estimated using ERA-Interim data through the definition of Wang et al (2004).…”

Section: Interannual Variability Of Bfa-m and Its Controlling Factorsmentioning

confidence: 99%

Interannual Variability of Baiu Frontal Activity in May and its Connectivity with June

Tomita

Yamaura

2020

Journal of the Meteorological Society of Japan

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The Baiu front (BF) is generally formed in May in the western North Pacific. Using objective analysis data from to (36 years), this study investigated the interannual variability of Baiu frontal activity (BFA) in May (BFA-M). In May, seasonal enhancement of warm and moist southerlies from the tropics climatologically establishes the BF as a largescale quasi-stationary front. The strength of the southerlies from the tropics also controls the interannual variability of BFA-M. The anomalous large-scale circulation centered around Taiwan, which can be interpreted as a moist Rossby wave from the equatorial Kelvin-Rossby wave packet in the western tropical Pacific, modifies the strength of the southerlies. The equatorial Kelvin-Rossby wave packet, which is identified as the equatorial intraseasonal oscillation (ISO), propagates eastward from the Indian Ocean to the western Pacific. The interannual variability of BFA-M has a biennial tendency, which stands in contrast with the three-year or four-year variation period of the El Niño/Southern Oscillation (ENSO). The biennial tendency is characterized by a zonal tripole distribution of sea surface temperature anomalies in the tropical Pacific, with corresponding anomalous Walker circulations. The induced anomaly fields are suitable for confining the disintegration of the equatorial Kelvin-Rossby wave packet in the western tropical Pacific and guiding the following northwestward propagation of the moist Rossby wave. With the phase reversal of ISO, the biennial tendency remains in the western part of the BF from May to mid-June, although the ENSO controls the BFA in the central part of the BF in June. This study proposes that the equatorial ISO in the Indian Ocean in April can be an indicator of BFA-M strength in the western North Pacific.

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Impacts of two types of El Niño on the MJO during boreal winter

Cited by 26 publications

References 31 publications

Tropospheric and Stratospheric Causal Pathways Between the MJO and NAO

Tropospheric and Stratospheric Causal Pathways Between the MJO and NAO

Combined effect of the QBO and ENSO on the MJO

Interannual Variability of Baiu Frontal Activity in May and its Connectivity with June

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